Air log



May 11, 1948. ANDERSON 2,441,381

AIR LOG Filed NOV. 27, 1943 10 Sheets-Sheet 1 MR SCOOP ATTORNEY May 11, 1948. E. P. ANDERSON AIR LOG Filed Nov. 2'7, 1943 10 Sheets-Sheet 2 .INVENTOR. gain/H80 I? HNDERSUN Y i E. P. ANDERSON 2,441,381

AIR LOG May 11, 1948.

10 Sheets-Sheet 5 Filed Nov. 27, 1943 B EaZzwrdPAzzdQsom AT TORNE) y 11, 19480 E. P. ANDERSON 2,441,381

AIR LOG Filed Nov. 27. 1943 10 Sheets-Sheet 4 52 I "f. 66 5 z L 5 74 1 l E E i IN VEN TOR.

BYlMWcZPAMsm A T TU/P/VE Y May 11, 1948. E. P. ANDERSON 2,441,381

AIR LOG Filed Nov. 27, 1943 10 Sheet-Sheet 5 IN VEN TOR.

BFMBAIZCQ'SOIL A TTORNE) May 11', 1948. E. P. ANDERSON 2,441,331

AIR LOG Filed Nov. 27, 1943 1Q sheets Sheet 6 65 INVEN TOR.

EdwmzlfiAmlersam ATTORNEY May 11, 1948.

E. P. ANDERSON AIR LOG Filed Nov. 27, 1943 10 Sheets-Sheet '7 IN V EN TOR.

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May 11, 1948. E. P. AN'DERSQN AIR LOG Filed Nov. 27, 1945 10 Sheetsfiheet 8 INVENTORB Arm/WU MANN v E. P. ANDERSON An LOG Filed Nov. 27, 1943 v 10 Sheets-Sheet 9 QNN INVENTOR. M00121 PA O [a ATTORNEY I May 11, 1948- E. P.- ANDERSON AIR LOG Filed Nov. 27, 1945 10 Sheets-Sheet 10 INVENTOR,

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ATTORNEY Patented May 11, 1948 UNITED STATES PATENT OFFICE AIR LOG Edward P. Anderson, Rutherford, N. 1., assignor to Bendix Aviation Corporation, Teterboro, N. 1., a corporation of Delaware Application November 27, 1943, Serial No. 512,013

1 13 Claims.

The present invention relates generally to air logs and particularly to a novel air mileage unit, such as may be used in systems for calculating air position or the like.

There are many methods of navigating and determining a mobile object's position, in combination with compass readings, from charts and tables based on computations involving functions such as, speed and distance. Calculations to determine air position or the like are usually made in knots" v(nautical miles per hour) for the reason that from a given position in azimuth of known latitude and longitude, a standard of set speed innautical miles per hour will permit reasonably accurate calculations of air position provided substantially accurate measurements of airspeed and air mileage are taken. Such calculations are possible because of the knowledge that 90 along the earth is 5,400 nautical miles. Actually, the definition of the nautical mile is, that it is one minute of latitude so that 90 90x60 5,400 minutes or nautical miles from the Equator to the poles. The earth is assumed for calculation purposes to be an exact sphere, although it is actually flattened at the poles.

Based on such knowledge, the air position of a craft for any instant may be determined from known functions of airspeed in nautical miles per hour from a position in azimuth and plotted on a chart, but the process of such calculations is laborious even for a trained navigator. Accordingly, numerous methods and apparatus for automatically determiningair position of a craft in degrees latitude and longitude have been devised with some degree or success, but where close calculations are required and/or at high speeds, such systems are not dependable due to unsatisfactory means for obtaining functions of distance flown and true airspeed of the aircraft.

It is, therefore, one object of the present invention to provide improved novel means for measuring the air mileage flown by means of a member functioning at a speed proportional to the true airspeed of the aircraft.

Another object is to provide a. novel means, whereby true airspeed measurement in minutes of latitude compensated for condition errors may 7 be transmitted to any suitable computer means Another object is to provide in a novel true Another object is to provide a novel system A employing a pump, such as a centrifugal air compressor having a controlled pressure output. for measuring true airspeed in nautical miles per hour.

Another object is to provide a novel airspeed metering system including means responsive to the differential in pressure between pitot static and impact pressures, and the system pump pressure to thereby control power means adapted to actuate the pump, so as to maintain balance between such pressures under all prevailing conditions of flight.

Another object is to provide a novel air pump for the purpose described, which isconstructed to dissipate compression heat, so as to maintain a more substantially constant temperature of air It is to be expressly understood, however, th'at the drawings are for the purpose of illustration only and are not designed as a definition 01 the limits of the invention. Reference for this latter purpose should be had to the appended claims.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Figure 1 is a side elevation of one form of the novel air log or air mileage pump unit of the present invention.

Figure 2 is a schematic illustration to show the location of the pump unit-and its connections with the control unit, relay amplifier circuit and atmospheric air.

Figure 3 is a diagrammatic illustration of the relay amplifier circuit.

Figure 4 is a bottom 'elevational view of the rotor chamber, showing an inlet cooling coil connected to the rotor shaft cap and an outlet nipple for connection to a control unit, as shown in Figure 2. I

Figure 5 is a view partly in cross section illustrating one form of pump rotor construction.

Figure 6 is a broken section view of the rotor shown in Figure 5, pulled apart.

Figure 7 is a longitudinal side section view of the overall pump housing with an elevatlonal view of the mechanism mounted therein.

Figure 8 is a top plan view of the overall pump housing,

Figure 9 is a longitudinal cross sectional view taken through both the pump overall housing and the pump rotor chamber.

Figure 10 is a cross-sectional view of one form of control unit mechanism removed from the casing.

Figure 11 is a front view partly in section of the control unit mechanism of Figure 10.

Figure 12 is a top plan view of the mechanism of Figure 11 taken along the line A-A thereof.

Figure 13 is a section view partly in elevation taken along the line 3-3 of Figure 12.

Figure 14 is a bottom plan view of the casing top for the mechanism shown in Figures 10 to 13.

Figure 15 is a front interior view of the casing with the top removed.

Figure 16 is a longitudinal cross section view of the casing with the top off.

Figure 17 is another form of control unit, wherein only one diaphragm is used.

Figure 18 is an exploded view of the several parts of the form shown in Figure 1?.

The air log or air mileage system of the present invention is composed on an air pump, such as best shown in Figures 1, 'I, and 9; control units, such as shown in Figures 10 to 18, and an amplifier and relay arrangement, such as is shown diagrammatically in Figure 3. Values of true airspeed can be obtained from this unit by any properly calibrated tachometer, and air miles can be determined by any properly calibrated counter. For example, the transmission between the pump and the tachometer used may be the usual flexible drive connection, which is rotated by the pump rotor, as hereinafter described, twenty-four (24) times for each nautical mile flown.

The several units of the present novel system will now be described in detail, reference being had first to Figure 9 of the drawings, wherein the novel air pump is shown. It includes an electric drive means, such as a series wound, D. C. motor 2|. The motor 2| drives the centrifugal pump rotor 22 in an airtight housing composed of upper and lower sections 23 and 24, through motor drive shaft 25 and rotor driven shaft 26 coupled together by coupling 21, which is made of suitable heat insulating material, such as phenolic ring or the like to prevent heat from the motor being conducted to the pump. Each rotor housing section 23 and 24 has a plurality of heat radiator fins 20 projecting outwardly from their respective outer surfaces.

The pump shaft 26 enters the pump housing section 23 through a suitable sealing gland, such as a graphite sealing gland, which consists of a graphite ring 30 mounted in an airtight flexible disc 3!. A nut 32 on the pump shaft 28 is threaded down, until its face is lightly bearing on the graphite ring 30, thus forming an air seal with a minimum of friction. The nut 32 may be locked by check nut 28.

The pump rotor 22 is a, substantially perfect annular flat integrally formed metal disc drilled through along the diameter to provide a diametrical conduit 34. This diametrical conduit 34 connects with a T-coupling conduit 35 run ning down the pump shalt At its lower end,

the pump shaft 26 passes through a second sealing gland 33, similar to the above described graphite ring 30 and flexible disc arrangement, and a metal cap 38 having cooling fins 31 is secured to the lower pump rotor housing section 24 by screws II or the like. A static air connection 40 is made to the inside of the cal) 36 by means of metal tubing 4|.

The static air from a suitable Pitot tube not shown, passes into tubing 41 at 83 and at 40 into cap 38, and then from the cap 36 through conduit 35 in the pump shaft 26 to the center of diametrical conduit 44 in the rotor 22 as shown by the arrows in Figure 9.

The pump shaft 25 is Journalled in bearings in sections 23 and 24 of the airtight rotor housing. The pump bearings, may be of a type such as ball bearings 42 and 43, one being located above the pump rotor 22 and the other below it. The bearings 42 and 43 may be protected by a disc 44 of suitable material, which fits over the bearing race. This bearing may float in its retainer to permit end thrust, if desired in any well known manner.

The rotor housing, comprises two shallow cup sections 23 and 24 secured together around the rotor 22, each carrying their respective bearings 42 and 43, above described. The lower section 24 is drilled below and adjacent the periphery of rotor 22 to provide an outlet conduit 45 for pump pressure, shown in Figure 7. leading to a threaded nipple 46 for transmitting the pressure developed in the pump to a suitable control unit, such as described hereinafter in connection with Figures 11 through 16 and in the modification shown in Figures 17 and 18.

Another form of construction wherein the rotor may be formed of two parts 46 and 41 is shown in Figures 5 and 6. Parts 46 and 41 are provided with grooves or channels 48' extending completely across a surface diameter thereof in radial alignment on either side of pump shaft 26 centrally disposed through the rotor. When parts 46 and 41 are assembled by suitable means, such as by welding, an elongated tubular channel 50 is defined thereby, runnin directly through the rotors inside diameter.

The motor 21 is mounted on support posts 52, which are part of the upper rotor housing 23, as shown in Figures '1 and 9. A mounting ring 52 of suitable heat insulating properties is located between the mounting lugs 54 on the motor 2| and the faced ends oi. posts 52, which serves to heat-insulate the pump rotor housing from the motor.

The main overall outer cover of the instrument is composed of three molded sections 55'. 55 and 56 of bakelite" or other desirable material. The top of cover section 55 is open to permit the motor 2| to extend upwardly therethrough and an auxiliary section or cap 55 is seated and sealed around the opening to close the top of the cover so that cooling air maybe circulated through the jacket or cover and around the compressor housing and drive motor 2|. Lugs 51 formed from the rotor housing sections 23 and 24 are used to mount and anchor the same in the bottom cover section 56, see Figures 4 and 7. The intermediate outer cover section 55 is then secured to the bottom outer section 56 by suitable fastening means such as, bolts 58, with a sealing gasket 59 between the sections to assure an airtight connection.

The lower section 56 of the main outer cover is provided with a relatively large inlet conduit and the upper section 55 is provided with an band on plug terminal 1|.

accuser outlet conduit 8|, as shown in Figure 8, whereby an additive cooling of the rotor housing is provided by circulation of cooling air around fins 28, and a relative temperature balance is maintained between the air in cooling-coils 8| connected to a Pitot static outer coupling 88, shown in Figure 1, in the lower cover section 58 substan tially in proportion to the air outside the pump.

The overall cover sections 85", 85 and 58 cup together, so as to form an outer casing around the pump rotor chamber, and the lower section 28 of the rotor housing may seat through lugs 51 on projections or shoulders 88 inside the lower section 58 of the overall casing, as shown in Figure 7. An opening in the lower section 58 may be provided, such as 85 for discharge of undesirable 6 ratio arm 81 rests lightly on a rigidly fixed bridge 88 on the Pitot diaphragm .82, as in Figure 12. The pivot 88 of the ratio arm 81 is mounted in the fork bracket, which is attached by means of a fastener such as screw 88 to a metal block 8|.- The position of the fork bracket 88 on block 8| is adjustable for calibration purposes, movement of the fork bracket 88 along the direction of the ratio arm 81 effectively changing the ratio of the arm. The metal block 8| is rigidly attached to a shaft 82 which rotates in bearings 88 and 88; one bearing is in the frame 88, and the other bearing is in the brass plate 88 which screws or otherwise fastens to the bottom of the frame 88. as shown in Figure 13. A contact arm 88 is secured to the shaft 82, the contact 81 carried by the arm 88 wiping over a smooth insulating block 88 with another contact 88 embedded in it. The whole lever system is lightly spring loaded by means of a hairspring I88 on the shaft 82. This arrangement keeps the ratio arm 81' lightly bear.-

ing on the bridge 88 of the Pitot diaphragm 82.

A low pressure must be applied to the Pitot diaphragm before the wiping contact 81 reaches 81 twenty-four (24) revolutions per nautical terminal 1| on the top of cover section 55, and

the negative lead 18, shown in Figure 1 as a metallic sheath for lead 88 insulated therefrom in the usual manner, is connected to a metallic The lead 18 is anchored to a post or terminal 12 on cover section 55 with suitable leads to the binding terminals of the motor 2| as shown in Figure '7. A double condenser and choke, generally designated 13 connected to the terminals of the motor 2| and leads 88 and 18 so as to be interposed between the leads and the motor, may be attached inside the top cover section 55 to provide high frequency suppression for the motor 2 I, see'Figure '1.

The entire pump unit is mounted on three mountings 14, such as double Lord type mountings or other well known anti-vibration mountings.

In lower section 58 of the pump unit cover are two threaded connections, such as static Pitot intake connection 88 connected to air cooled coil II and pump outlet connection 48 connected to a diaphragm of a control unit, as hereinafter described. Each connection 83 and 48 is sealed in the section 58 by sealing members 18 and 11, as shown in Figure 1.

The pump unit is connected to a control unit mounted in an airtight'casing' 88 see Figures 14, 15, and 16; one form being illustrated in detail in FigureslO, 11, 12 and 13 of the'drawings. This unit is composed of two similar diaphragms 8| and 82 matched together and'interchangeably mounted in pairs on a frame 88.

Pitot pressure is connected to the diaphragm 82-which directlyoperates a ratio lever 81, and pump pressure is connected to the diaphragm 8| which operates a link 85 connecting with the lever 81. The Pitot pressure'may' enter through any suitable dual coupling, such as'18. A light metal split stud or fork 18 is rigidlyilxed to the pump diaphragm 8|, and the link 85 is hinged in the stud 18.

At its other end, the link 85 is hinged within a fork bracket 88 to one end of ratio arm 81, thereby providing a differential linkage with approximately a 1:3 ratio. The other end of the the contact 88 in the insulating block 88. This pressure represents the cut-in" speed of approximately miles per hour at which the pressure in the Pitot tube will actuate bellows 82 to operate the pump motor 2|. If, after this speed has been reached the ratio of displacement of diaphragm 82 to diaphragm 8| is equal to that ratio of lever 81 to link 85, no motion will be transmitted through pivot 88 to the fork 88. Therefore, the shaft 82 will not rotate nor will the wiping contact 81 move. It is contact 81 is about 3:1 (speed is proportional to V pressure).

This is true since the ratio of movement of the shorter arm of lever 81 by the link to the longer arm of said lever is about 1 :3.

Because the speed displacement curves for the diaphragms 8| and 82 are not accurately linear, and because the diaphragms do not work over equal displacements, the pump would tend to run slow at high speeds, i. e., the diaphragm characteristics are such that the error which would arise owing to the lag in static pressure compressibility effect at such high speeds is over-corrected. This effect is corrected by means of a light leaf spring I8I, best shown in Figure 12, which biases the extension of pump diaphragm 8| by resting on the diaphragm bridge I82. A series of threaded stops generally designated by numeral I83, which effectively vary the spring rate and force over the range of displacements of the diaphragm 8|, are used for calibration purposes.

The insulating block 88 containing the fixed contact 88 is pivoted about a bolt I84, and its position is adjustable by means of an eccentric I85, Figure 10, which shifts the position of the opposite end of this block 88. The eccentric I85 is defined longitudinally around the split inner end of bolt |85a which snugly engages in a slotted or forked end of the block 88 to adjust the position of the latter and relation of the contacts 81 and 88 and avoid lost motion or play. A head I88d on the bolt is countersunk in cover I90, and is held countersunk within the cover I by expansion spring 8 between the cover and washer I051) seated over radial pins IOIc extending through the bolt or pin IOBa. The adjustment affects both the cut-in" speed and the calibration of'the unit and is accessible from outside the casing through bolt head I00a which is sealed over with wax I after calibration, which seal must be broken for any readjustment.

A bi-metal rod I01, Figure 11, bearing on the pump diaphragm mounting bracket I00, compensates for temperature changes.

The entire mechanism is mounted in the "bakelite" housing 90. The main cover I09 is also of "bakelite." and a gasket between both cover and housing makes the interior airtight, as shown in Figures 14 to 16.

Static pressure is introduced intothe housing 09 and around the diaphragms through the threaded bushing I09 in the rear of the housing. Two other bushings, H0 and III, are provided for pump and Pitot pressure connections.

The wiping contact 91 is connected to the ing or terminal post H2 and wire II! on the plate 95 through shaft 92 and spring I00, and the fixed contact 99 is connected to a one-pin plug I I9 and wire IIIi. Lug H2 and plug II! are arranged to coincide with openings H211 and 3a, respectively, in the cover I00.

Four mounting holes I are provided. It is not essential that the unit be secured on a shockproof mounting, but the instrument must be mounted so that the diaphragms 0| and 82 are in a vertical plane to minimize the effects of position error.

In Figure 3 is illustrated an amplifier and relay circuit connected between the motor M for driving the pump rotor 22 and the control unit contacts 91 and 99, for example.

This circuit contains a gas filled tetrode having a control grid I22 and a plate I23. From a suitable rectifier power source positive lead 1 is connected to the plate I23 and by wire I I5 to the stationary contact 99 of the control unit. Power lead II! is further connected to a relay contact I20. A second relay contact I2l adapted to be connected to the contact I20 upon movement of the relay switch arm, is connected to the positive terminal 69 of the pump motor 2|. The pump motor 2i is further connected by wire I0 to the negative (grounded) power lead I II! of said power source. Connected inv parallel across the relay contacts I20 and I2I is a spark suppression circuit comprising a resistor R2 and a condenser C2.

To control the device as hereinbefore set forth, movable contact 91 is connected to terminal lu H2 and then by wire IIS through a resistor R3 to the negative power lead I18. Lead H8 is further connected through a resistor RI to the control grid 522 of said tetrode. Said control grid is further connected to the negative power lead through a condenser CI. Connected across the power leads ill and III! is a variable resistor R, the tap-off of said resistor being connected through a relay coil adapted to control the closand opening of contacts I20 and HI, to the cathode of said gas filled tetrode.

Condenser C1 and resistance 31 provide a time delay on pick up to prevent the relay contacts and iii from closing in response to fluctuations produced by vibrations in the control unit diephragms 8i and 32. This reduces the number of impulses and interruptions in the circuit to the drive motorfli and thus the fiuotuatioi s 8 the pump rotor 22 while maintaining a balance between the pressures in the diaphragm 0| and When control contacts 91 and 99 close, the voltage across resistance R: immediately becomes full line voltage instead of zero, but the voltage of grid I22 rises slowly owing to the time required to charge condenser C1 through resistance R1. when the voltage of grid I22 approaches line voltage, the current in plate I22 increases sufficiently to energize the relay to close contacts I20 and III. when the contacts open again, the voltage in grid I22 drops slowly owing to discharge or condenser 01 through resistances R1 and Rs.

After the voltage in grid I22 drops to appproximately two volts. the current in plate I22 becomes insuflicient to hold the relay energized. A variable resistor R is used to provide a small amount of fixed bias on the tube in order to reduce the plate current below the drop-off value of the relay when the contacts 91 and 89 open. A condenser Ca and resistor R2, may be provided as a relay arc quencher for the relay contacts I20 and I2I,if desired.

The operation of the system should be apparent from the foregoing description, and briefly the principle involved in the operation of the air mileage unit is the balancing of Pitot pressure against pressure developed by a centrifugal pump rotor operating from static pressure and rotating in an airtight casing.

Pitot pressure, developed in the Pitot tube, is equal to lMV (neglecting compressibility) where M is the air density and V is the true airspeed of the aircraft.

Pump pressure, developed by a centrifugal pump, such as described, is proportional to ,MiVi, where M1 is the air density at the center of the pump, and V1 is the rate of rotation of the rotor periphery.

If the speed of pump rotor 22 is controlled to maintain a balance between Pitot pressure and pump pressure, and the density of the air at the center of the conduit 34 in pump rotor 22 equals the density of the air outside the aircraft, then the rate of rotation of the pump rotor will be proportional to the true airspeed of the aircraft. The two densities are kept equal with the pressure at a constant ratio, by connecting the center of the pump rotor 22 through conduit 25 in the pump shaft 28 to a source of static pressure 63, see Figure 1, and by maintaining the air inside the pump at outside air temperature by inducing a flow of air around the pump housing from outside the aircraft while simultaneously compensating for or dissipating compression heat assisted by the fins 20.

Thus when the speed of the rotor is such that its pressure output in diaphragm 8| exceeds the impact Pitot pressure in diaphragm 82, the relay contacts I20 and HI are broken through the separation of control unit contacts 91 and 99, to thereby deenergize the motor 2|, so that during flight the motor 2i is constantly energized and deenergized for intermittent periods to keep the number of rotor revolutions per hour closely corresponding to the airspeed of the craft carrying the same.

Another form of control unit is shown in Figures 17 and 18 mounted in an airtight casin H0. It comprises a pressure responsive member, such as diaphragm lei interiorly connected to the pump outlet 55 at the nipple or connection :16 in the lower sections 26 and 56 of the air pump rotor housing and cover through conduit 45, see Figures 7 and 9. The diaphragm MI is mounted on a frame I42 secured therein, as by the coupling nipple I43.

Leading into housing I40 is another conduit I44 connected to a Pitot tube, not shown, whereby a differential in the pressure relation between pump pressure and Pitot impact pressure will actuate the diaphragm I4I.

The frame I42 may be shaped as a rectangle having an ofl-set curved part over the front of diaphragm I at a point ofl-set with respect to the center bridge or loop I45 thereof, so as to provide arms I46 and I41 on each end of the curved part. Arms I46 and I41 are designed to ,mount the diaphragm actuated parts, hereinafter described.

Arm I41 supports a linkage system operated by diaphragm loop I45, which engages a crank lever or upright arm I48 fastened to one end of a slotted arm I49a of a spring bracket I48 secured to a. rock shaft I49, which is journalled at its ends. On the inner end are bearing screws I49 adjustable in rods I50 and II depending from V-bracket I52 which in turn is secured by bolt I53 in elongated slot I54 to lug I55 of arm I41. The slot of the arm I49a receives the upper bearing screw I49 and a screw I48b serves to adjust the bracket and arm so that the lever or arm I48 will properly engage the bridge or loop I45 to respond to the movements of the diaphragm I4I.

Extending upward from the other end of rock shaft I49 is rod I56, which in turn engages rod I51 extending at substantially right angles from hairspring shaft I59, to which an end of hair-- spring I59 is attached. The other end of the hairspring coil I59 is attached to the frame I 42.

On shaft I58 spaced from rod I51 is movable contact arm I60 with a counterweight I 6i on the extremity to one side of the hairspring shaft I58, and a contact point I62 on the other extremity connected to the wire I I6.

Cooperating with the point I62 of arm I60 is an adjustable insulation or bakelite contact block I63 carried by the free end of'curved arm I64 adapted to swing on pin I65 secured in the under side of flat top bar I66, which is secured to lugs I61 on frame I42, as by screws I68.

Adjustment of block I63 is accomplished by screw or bolt I69 swiveled in one end of the block I63, and threadable through bracket I secured to top bar I66, as by screws I1I. Such adjustment will be necessary in high speed ships, so as to set for zero speed in roportion to the added weight of the compressed air within the centrifugal pump.

The diaphragm arran ement is set so that contraction thereof will close a circuit through contact arm I60 grounded to the frame I42 through which connection is made to the wire H6 and I contact I12 embedded in the block I63 is connected in a relay circuit substantially as shown in Figure 3 through wire I I5, which in turn suparm I60, which are controlled by diaphragm means I to break the circuit to motor 2I and to deenergize the same, so that during flight the motor 2I is constantly energized and deenergized for intermittent periods dampened or reduced by the time delay system above described to keep the revolutions of the rotor per hour closely corresponding to the speed of the craft,

The control unit of this form differs from the first form by providing only one diaphragm for maintenance of pump pressure to match the Pitot pressure, such Pitot pressure being maintained as representative of the air velocity about 1 the ship. By constantly matching the representative Pitot pressure with pump pressure, the speed of the pump will be directly related to the airspeed in substantially the same manner as described in the operation of the first form of unit.

There is thus provided a novel arrangement and apparatus for determining air mileage and true airspeed with a novel air pump, the speed of rotation of which is suitably controlled, as by the novel units described in proportion to static pressures fed into the center of the rotor at inlet 63 and into part of the control unit at a temperature corresponding to the temperature of the air outside the aircraft, to thereby actuate a control adapted to maintain a balance between Pitot pressures, and the pum pressure; so that the speed of the pump rotor increases or decreases with respect to the time required to restore balance between the pump and Pitot pressures following each change in the Pitot pressures, based on the fact that the rotor revolves twenty-four times for each nautical mile travelled in proportion to such changes in Pitot pressures brought about by the projection of an aircraft through the atmosphere.

Although only several embodiments of the invention have been illustrated and described, other changes and modifications, which will now appear to those skilled in the art, may be made without departing from the scope of the present invention. Reference is, therefore, to be had to the appended claims for a definition of the limits of the present invention.

What is claimed is:

1. An air log for determining the airspeed of an aircraft comprising in combination, a compressor having an air compressioned chamber, an inlet and an outlet for said chamber, said inlet being connected to a source of static pressure leading to the center of said chamber; an outer jacket for said compressor, an inlet and an outlet for said jacket in communication with the atmospheric air outside the craft on which the device is mounted, a vacuum nozzle for said outlet, said atmospheric air in said outer jacket serving to cool said air compression chamber, an impact pressure source outside of the craft, and intermittent drive means for the compressor responsive to the differential between compressor outlet pressure and impact pressure derived from said impact pressure source outside said craft to thereby govern the speed- 0f said compressor in proportion to the speed of the aircraft, said drive means having means to dampen fluctuations in the operation of the compressor.

2. Means for determining the airspeed of a craft comprising, an electrically driven compressor having an inlet and an outlet, said inlet being connected to a, source of static air pressure, a casing for said compressor having an inlet connected to a source of static air pressure and an outlet. provided with a vacuum nozzle in the slip stream of said craft, to maintain a substantially constant temperature balance between the static air pressure inlet and compressor pressure outlet, and the air surrounding said crait, means responsive to pressures discharged from said compressor, means connected to an impact air pressure source and responsive thereto, and means intermediate said responsive means to make and break an electrical circuit to said electrically driven compressor in proportion to the impact pressures developed in accordance with the speed of said craft to maintain a balance between said pressures.

3. In a device for determining airspeed, in combination with a suitable source or Pitot pressure having a static pressure line and an impact pressure line, a pressure controlled diflerential unit open to static pressure, a mechanical pressure chamber, an impeller in said chamber having a peripheral outlet, an impeller shaft, an inlet extending axially or said shaft to the axis of said impeller connected to said static pressure line and said outlet, an outlet coupling in said chamber adjacent the periphery of said impeller connected to said diflerential unit from said pump outlet, a casing for said compression chamber having an inlet and an outlet, said inlet being connected to a source of static air pressure. said outlet being provided with a vacuum nozzle to circulate the air about said compression chamber, and drive means for said impeller controlled by the diflerential between pump pressure and impact pressure with respect to static pressure in said diflerential tmit.

4. An air pump {or use in systems of the class described, comprising a rotor having a diametrically positioned exhaust conduit therethrough, a rotor chamber, a shaft having an axial intake defined therein extending to the conduit, a housing around said rotor chamber having an inlet and exhaust to atmospheric pressure, said exhaust being provided with a vacuum nozzle, an inlet conduit connected to said shaft intake from a suitable source of Pitot static pressure, and an outlet coupling adjacent the periphery of said rotor in said rotor chamber, said vacuum nozzle, housing and housing inlet being adapted to maintain the static pressure fed into the pump at a temperature substantially equal to the temperature of outside atmospheric air.

5. An air pump for use in systems of the class described, comprising a rotor having a diametrically positioned exhaust conduit therethrough, a rotor chamber provided with heat dissipating fins, a shaft having an axial intake defined therein, a. housing around said rotor chamber having an inlet and exhaust to atmospheric pressure, a vacuum nozzle tor said exhaust, an inlet coil coupled to said rotor shaft intake from a source of static pressure mounted in said housing adjacent said atmospheric inlet, whereby the air in the housing around the heat dissipating fins and the static air inside said cell are cooled substantially to the temperature oi atmospheric air outside the housin to compensate for density changes caused ssion heat.

iiugal air log for measuring functions of airspeed in combination with a drive means and a conacl 1 hit for said drive means, comprising a housing, irlet for said housing and an outlet provided with a nozzle to circulate air through housing, an air compression chamber mounted in said housing having heat radiating fins extending tliereirom in the path of said circulating air, a rotor in said chamber,

pressure outside said housing and disposed in the path of said circulating air, a pump shalt having an axial intake conduit therein connected to an end 01 said coil, to thereby deliver static air to the center oi said rotor at a temperature substantially equal to atmospheric air, and an outlet coupling in said rotor chamber adlacent the periphery of said rotor connected to said control unit, to thereby control said pump drive means according to pressure values or the pump outlet and Pitot impact pressures as a function of airspeed.

7. A system for balancing a pump pressure output with a variable velocity pressure condition generated in accordance with the airspeed of an aircraft comprising an air pump, an electric mo tor for driving said pump, pressure switch means responsive to an unbalance between said pressures adapted to intermittently energize and de-energize said pump driving motor, and a relay circuit interconnected between said electric motor and said switch means, an amplifier tube having a plate and a control grid in said circuit with said switch means, a relay operated switch connected to the plate circuit of said tube and to said pump driving motor; operation of said pressure switch biasing said control grid to operate said tube, the resulting current in said plate circult actuating said relay switch to operate said pump driving motor to maintain balance between pump'pressures and velocity pressures in accordance with the airspeed of the aircraft.

8. A controller comprising, a rotatable shalt, a member fixed thereto, a lever pivoted to said member, one end or said lever being adapted to be moved by a linear force; a link, adapted to be moved by asecond force, pivoted to the other end of said lever to balance said first force; a contact fixed to and movable with said shaft, and a stationary contact adapted to be engaged by said movable contact upon rotation of said shalt due to an unbalance of the two applied iorces.

9. A controller comprising, a rotatable shalt, a member fixed thereto, a lever pivoted to said member, one end 0! said lever being adapted to be moved by a linear force; a link, adapted to be moved by a second force, pivoted to the other end of said lever to balance said first force; a contact fixed to and movable with said shalt, a stationary contact adapted to be engaged by said movable contact upon rotation of said shaft due to an unbalance of the two applied forces, and a temperature responsive element to correct the movement of said link during ambient temperature changes.

l0. A controller comprising, a rotatable shalt, a member fixed thereto, a lever pivoted to said member, one end or said lever being adapted to be moved by a linear force; a. link, adapted to be moved by a second force, pivoted to the other end of said lever to balance said first force; said first and second forces being of unequal magnitude, the lengths of the arms of said lever being in the same ratio as that 01' the two unequal l forces, a contact fixed to and movable with said shaft, and a stationary contact adapted to be engaged by said movable contact upon rotation of said shaft due to an unbalance oi the two applied forces.

ii. A. controller comprising, two opposed pres sure responsive members adapted to be actuated respectively within two disproportionate pressure ranges, a rotatable shaft therebetween, a forked member fixed thereto; a lever pivoted to coil mounted in said housing connected to static said one end of said lever being adapted to be moved by the pressure member actuated within the higher pressure range, the ratio of the lengths or the two arms of said lever being of the same order as the ratio of the square roots of the two pressures applied; a link pivoted at one end to the other end of said lever adapted to be moved by the other of said pressure members to balance the pressure actuating said first pressure member, a contact fixed to said shaft and rotatable therewith, and a stationary contact adapted to be engaged by said movable contact upon rotation of said shaft due to an unbalance of the applied pressures.

12. A controller comprising, two, opposed pressure responsive members adapted to be actuated respectively within two disproportionate pressure ranges, a rotatable shaft therebetween, a, forked member fixed thereto; a lever pivoted to said forked member, one end of said lever being adapted to be moved by the pressure member actuated within the higher pressure range, the ratio of the lengths of the two arms of said lever being of the same order as the ratio'of the square roots of the two pressures applied; a link pivoted at one end to the other end 01' said lever adapted to be moved by the other of said pressure members to balance the pressure actuating said first pressure member, variable resilient means asso-' ciated with said second pressure responsive member for correcting the linear displacement of said member, a contact flxed to said shaft and rotatable therewith, a stationary contact adapted to be engaged by said movable contact upon rotation of said shaft due to an unbalance of the applied pressures, and a temperature responsive element to correct the linearmovement of said second pressure responsive element for ambient temperature changes.

13. Means for determining the speed of a. craft comprising a pump connected to a suitable source of static pressure, a motor for operating said pump, a pressure responsive member connected to a suitable source or impact pressure, a pressure responsive member connected to said pump, a differential linkage interconnecting said pressure responsive members and balanced thereby, a switch actuated by the movement of said linkage upon an unbalance thereof by said members, a relay circuit controlled by the actuation of said switch to operate said motor for increasing the pressure delivered by said pump to said second member for rebalanclng said linkage, and means included in said relay circuit to delay motor op eration upon the actuation of said switch.

.EDWARD P. ANDERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,444,403 Varley Feb. 6, 1923 1,451,064 Dunajefl 1 Aug. 10, 1923 1,518,279 Smoot Dec. 9, 1924 1,522,321 Lea Sept. 1, 1925 1,592,613 Meyer July 13, 1926 1,677,835 Linderman July 17, 1928 1,842,238 Benesh Jan. 19, 1932 1,867,225 Le Van et a1. July 12, 1932 1,909,471 Kelly May 16, 1933 1,942,587 Whitman Jan. 9, 1934 1,942,913 Begg Jan. 9, 1934 1,954,425 Place et al. Apr. 10, 1934 2,031,502 Powell Feb. 18, 1936 2,062,045 Van Devanter Nov. 24, 1936 2,177,244 Ciamberlini Oct. 24, 1939 2,269,068 Corbin Jan. 6, 1942 2,357,199 Holst Aug. 29, 1944 FOREIGN PATENTS Number Country Date 179,903 Great Britain Feb. 15. 1923 353,994 Great Britain Aug. 6, 1931 571,753 France Feb. 8, 1924 

